The blue mussel inside: 3D visualization and description of the vascular-related anatomy of Mytilus edulis to unravel hemolymph extraction

Abstract

the blue mussel Mytilus edulis is an intensely studied bivalve in biomonitoring programs worldwide. the lack of detailed descriptions of hemolymph-withdrawal protocols, particularly with regard to the place from where hemolymph could be perfused from, raises questions regarding the exact composition of aspirated hemolymph and does not exclude the possibility of contamination with other bodyfluids. This study demonstrates the use of high resolution X-ray computed tomography and histology combined with 3D-reconstruction using AMIRA-software to visualize some important vascular-related anatomic structures of Mytilus edulis. Based on these images, different hemolymph extraction sites used in bivalve research were visualized and described, leading to new insights into hemolymph collection. Results show that hemolymph withdrawn from the posterior adductor muscle could be extracted from small spaces and fissures between the muscle fibers that are connected to at least one hemolymph supplying artery, more specifically the left posterior gastro-intestinal artery. Furthermore, 3D-reconstructions indicate that puncturing hemolymph from the pericard, anterior aorta, atria and ventricle in a non-invasive way should be possible. Hemolymph withdrawal from the heart is less straightforward and more prone to contamination from the pallial cavity. this study resulted simultaneously in a detailed description and visualization of the vascular-related anatomy of Mytilus edulis. Bivalve hemolymph is extensively used in a range of research domains such as ecotoxicology 1 , ecophysiology 2 and (immune)toxicology 3. Mytilus edulis (M. edulis Linnaeus, RRID:SCR_006069) hemolymph is also widely used in bio-accumulation and environmental studies concerning heavy metals such as cupper, mercury and cadmium 4-6. Mussels are sessile filter-feeders: they continuously filter the surrounding water, making them excellent model organisms for eco-toxicological and eco-physiological studies. For example, studies on the uptake, fate and biological consequences of ingested microplastics 2,7 , toxicity assays with heavy metals 1 and immunotoxic research 3 all depend on the collection of hemolymph. Depending on the nature of the research, hemolymph extraction techniques vary from invasive (lethal) to non-invasive procedures and from single to multiple withdrawals. The main hemolymph collection site in bivalves is the adductor muscle (anterior or posterior, depending on the

Multi‐residue extraction to determine organic pollutants in mussel hemolymph

“…Hemolymph composition is different depending on the tissue and it is not clear where the fluids come from when it is extracted from the posterior adductor mussel. However, Eggermont et al [27] suggest that this hemolymph could be from small spaces and fissures between the muscle fibers that are connected to the posterior gastro-intestinal artery. The volume extracted was between 0.2-0.5 mL depending on the specimen.…”

“…The hemolymph of these bivalve mollusks (the invertebrate equivalent of mammalian blood) is an attractive bio-fluid in contact with different tissues to assess biomarker responses to contamination, because it can report about the functional status of the organs which are perfused but lacks the molecular complexity of whole organ tissues [25]. Mussel hemolymph has a very variable proportion of minerals, proteins and cells depending on the tissue and the specimen [26,27], which make it a complex matrix. However, up to our knowledge, analytical methods to determine contaminants in hemolymph have not been reported yet.…”

Rapid Domoic Acid Depuration in the Scallop Argopecten purpuratus and Its Transfer from the Digestive Gland to Other Organs

“…The fast depuration rate estimated for Mu could be explained by the fact that the adductor muscle contains a large amount of hemolymph in venous sinuses and an important artery [50]. This organ is in fact the most adequate one to extract hemolymph from bivalves [51]. DA transfer from visceral to other tissues through the circulatory system has been suggested in the oyster Crassostrea gigas [52].…”

Phosphatized adductor muscle remains in a Cenomanian limid bivalve from Villers-sur-Mer (France)

“…The adductores are usually differentiated in two parts that correspond to two different functions: (1) quickly contracting to close the valves under threat (quick muscle; fast, strong and short) and (2) keeping the valves closed firmly (catch muscle; slow, continuous, e.g., Bowden, 1958 ; Millman, 1967 ; Chantler, 2006 ; Simone, 2019 ; Eggermont et al, 2020 ; Castro-Claros et al, 2021 ). Accordingly, these muscle fibres can be differentiated functionally and morphologically into striated muscular fibres and smooth fibres.…”